爬行空间楼层
New home, currently near end of design phase, zone 2, highly expansive clay soil. The current plan is a closed crawl space with 4′ between crawl space floor and finished first floor. However, the crawl space floor will be about 12″ above natural grade, so first floor elevation will be about 5′ above natural grade. The height is a good thing for the aesthetics of the house (southern Louisiana style house with wide, deep covered porches at front and rear of house).
Since crawl space foundations haven’t been used in my local area for decades, and all the older ones are vented, this foundation will be very “unusual” for this area, and expertise for it is certainly lacking. I’ve been reading about these foundations for months to get a good understanding of them. Some of the designs I’ve seen that contain a concrete crawl space floor call for a thin slab, sometimes without steel. I’ve seen them called “rat slabs”. My foundation engineer has specified a 2″ thick slab that is referred to on the drawings as a 2″ concrete skim coat. The engineer confirmed that it doesn’t have any steel in it. The plan also calls for 90 drilled shafts for the home (3300 sqft plus 3-car attached garage).
我喜欢混凝土爬行空间地板的想法（如果我能负担得起），但我的担忧是由于膨胀性粘土土壤将迅速破裂。Yes, about a foot of select fill will be brought in which will be between the crawl space floor and the clay soil, but it will compacted so I don’t think it will keep the upheaval forces from the clay soil from cracking the crawl space floor. The engineer agrees. I should note that even though he is experienced with crawl space foundation designs, most of the ones he has done are either vented and/or don’t have a concrete floor.
Is there a solution for this which includes a concrete crawl space floor, or should I give up on this detail and just put a water/vapor/air barrier on the ground and let that be the “floor”? It looks like the only solution for a concrete floor that won’t crack is to build something similar to a “regular” structural slab with void cartons, then build the crawl space on the slab.
谢谢，
Ira
Replies
They're called "rat slabs", because a primary purpose/function of the non-structural slab is to prevent burrowing rodents from gaining entry. What intended function or purpose are YOU looking for the slab to provide?
A chicken-wire reinforced 2" rat slab wouldn't keep it from cracking, but will limit how fast the crack propagates &/or separates.
通过一个1-2“水平的沙子，在蒸汽屏障上，2”厚实的混凝土庭院摊铺机的楼层是一个相对干净的可行性/爬行的啮齿动物抗底板，不受膨胀土的影响。如果它升起并随着时间的推移，它可以根据需要重新升级。这通常比2英寸倒的鼠比例更昂贵。
Rat slab was a bit of a misnomer for my neighbour Chuck. He had a bear tunnel into his crawlspace to hibernate.
>"He had a bear tunnel into his crawlspace to hibernate."
DAMN! Some of those pesky critters can be PUSHY! In areas where the frost depths and footings would be deeper than yours it would be an enormous amount of digging.
我想到当地的害虫控制公司不想触摸那个！？:-)
“板坯”开发裂缝没有什么问题。混凝土似乎是为了保护它下方的水/蒸汽/空气屏障，所以裂缝只是美学。如果他们打扰你，你可以完全走得更厚或省略混凝土。
如果您要使用爬行空间进行存储，或者害虫是一个潜在的问题，那么将某些东西放在多个上是一个可能的好主意。木材也是一种选择;这里可以找到有关该的更多信息（以及地下室中的板坯的功能）：//m.etiketa4.com/article/do-i-really-need-a-concrete-basement-floor
As the other guys said the concrete is not structural. It's only there to protect your poly just below. Don't want to walk on the poly and puncture it with holes.
伊拉伊阿拉，
Another vote for what we call a Scratch Coat up here. There is a vast difference in usability of a crawlspace with a concrete floor compared to one with just poly.
请注意，当您将房屋和塑料放过它时，膨胀土变得较小，减少极端水分。您甚至可能将区域延伸到基础之外的地下屋顶。